Method and apparatus for concen



5 Sheets-Sheet l INVENTOR. v C W705) W. C. MAST Original Filed SeptMETHOD AND APPARATUS FOR CONCENTRATING SULPHURIC AGID Jan. 23, 1934.

BY M 45 0 ATTORNEYS Jan. 23, 1934. w. c. MAST 19,064

METHOD AND APPARATUS FOR CONCENTRATING SULPHURIC ACID Original FiledSept. 22/ 1927 3 Sheets-Sheet 2 Z5. fig 47 A TTORNEY-S' 22, 1927 3Sheets-Sheet 5 INVENTOR. 1447/1210! 6 Maw-r W. C. MAST Original FiledSept METHOD AND APPARATUS FOR CONGENTRATING SULPHURIC ACID Jan. 23,1934.

BY M w ATTORNEYS Reiaued Jan. 23, 1934 UNITED STATES METHOD ANDAPPARATUS FOR CONCEN TRATING SULPHURIC ACID William-C. Mast, Long Beach,can, assignor, by mesne assignments, to Chemical ConstructionCorporation, a corporation of Delaware Original No. 1,790,507, datedJanuary 27, 1931, Serial No. 221,157, September 22, 1927. Applicationfor reissue April 16, 1931. Serial No.

15 Claims. (Cl. 323-171) This invention relates to the concentrating ofliquids, especially sulphuric acid, and is particularly intended forconcentration of sludge acid, that is to say, the acid recovered fromthe sludge resulting from the usual acid treatment of hydrocarbon orpetroleum oils.. While certain of the advanta es of the process are morepronounced in the case of sludge acid concentration, the invention is,however, applicable'to sulphuric acid concentration in general.

The main object of the invention is to provide a more economical andeffective process and apparatus for concentrating sulphuric acid thanhave heretofore been in use.

Further and more particular objects of the invention are to provide forcomplete and eflicient utilization of the available heat in the hotgases used for effecting the concentration, to permit the use of anapparatus having a lower first cost as well as a minimum cost of maintenance due to the practically indestructible construction thereof, toprovide for absorption of acid vapors by bubbling the gases passing froma more concentrated portion of acid through a less concentrated portionof acid, thereby eliminating expensive absorption towers, tosubstantially eliminate all leakage of fumes from, the concentrator andto permit a high degree of accessihility to all parts of the apparatus.

The method by which these operations are accomplished consists brieflyin maintaining a plurality of bodies of acid defining a plurality ofstages, continuously passing acid through said bodies or stages insuccession, and causing a stream of hot gases to be successivelydelivered, preferably under pressure, beneath the surface of therespective bodies of acid so as to bubble upwardly therethrough, thegases after passing through one of said bodies of acid being deliveredto and bubbled through-another body of acid and so on. The direction offlow of hot gases through the successive bodies of acid is, in general,preferably counter-current to the direction of flow of' acid, althoughsome departure may occasionally be advantageously made from thisprocedure, as hereinafter described. In the case of straightcounter-current flow the hot gases pass first through the body of mostconcentrated acid, then to the preceding body of acid containingslightly weaker acid and so on until they are finally passed through thedilute acid.

This process maybe carried out in a single horizontal cylindrical steeltank or drum, lined most with lead and acid-resisting brick, and parti-I tioned into a number of compartments through other, or it may consistof a combination of these two schemes, or any other suitabe arrangementof chambers for accomplishing the same result.

The use ofcylindricaltanks lined with lead and acid-proof brick is,however, of particular advantage, since the cylindrical constructionmaintains the bricks tightly in position at all times and preventschecks and leakage of acid and fumes, which is inherent in other typesof concentrating plants. Furthermore, these tanks ;will last practicallyindefinitely and minimize the maintenance cost.

It may be seen that as the hot gases pass from each stage or body ofacid to the next they con- I tain acid vapors carried off from the bodythrough which they have just passed. By delivering these gases beneaththe surface of a body of weaker acid, which is also cooler, these strongacid vapors are caused to be largely absorbed in such cooler and weakeracid. The acid vapors passing from this weaker acid, are delivered, inturn, with the gases, beneath the surface of a still weaker and cooleracid and are again absorbed. As no acid is evaporated and only watervapor is driven off.

when the acid has a concentration of less than 1315., no acid fumesoriginate in the last body of acid through which the gases pass, andsince as above described the acid fumes from the preceding bodies ofacid are substantially all absorbed, the exit gases are substantiallyfree from acid, containing only such particles as are carried overmechanically in suspension and which can be removed by suitable meanssuch as a small scrubbing tower or box.

An important advantage of this method consists in the releasing of thehot gases beneath the surface of the acid so as to provide a largesurface for evaporation of water therefrom and to also agitate the acid.The increased rate of evaporation obtained in this manner permitsconcentration to be effected at the same rate as though the boilingpoint were actually lowered more than F. below its true boiling point atthe prevailing pressure; and the lower temperatures which may thereforebe used minimize decomposition of acid and facilitate absorption of acidfumes in the successively weaker and cooler a certain proportion ofexcess air. and such hot gases may be produced in any suitable type offurnace or combustion apparatus.

While, as above stated, the direction of gas flow is preferably ingeneral counter-current to 'the flow of acid, it may be found desirablein some cases, especially when impurities are present (as inconcentration of sludge acid), to pass the hot gases first through acompartment of less concentrated acid and then pass the partly cooledgases through the body of strongest acid, so as to prevent decompositionof the strong acid by the hot gases in the presence of such inspurities.

The accompanying drawings illustrate apparatus which is suitable forcarrying out the above described operations and which also forms a partof the present invention. Referring to these drawings:

Fig. 1 is a partly sectional plan view of one form of such apparatus.

Fig. 2 is a section on line 22 in Fig. 1.

Fig. 3is a transverse section on line 3-3 in Fig. 2.

Fig. 4 is a section on line 44 in Fig. 1.

Fig. 5 is a section on line 55 in Fig. 1.

Fig. 6 is a longitudinal section of a modified form of apparatus.

Fig. 7 is a longitudinal section of another modiflcation.

Fig. 8 is a section on line 88 in Fig. 7.

The apparatus shown in Figs. 1, 2, and 3 comprises two horizontalcylindrical steel tanks 1, each of which is provided with a lead lining2 and also with a lining .3 of acid-resisting brick within said leadlining, said acid-resisting brick being laid up in acid-resisting cementto prevent corrosive action of the hot acid on the metal. Each of thesetanks is divided by a partition 5 into two chambers or compartments 6,said compartments being numbered 6a, 6b,-6c, and (id in the order inwhich the acid passes therethrough in the case of straightcounter-current flow. The acid may be delivered to chamber 611 by meansof pipe 8, thence'by means of pipe 9a, over-flow device 10a, and pipe11a to chamber 6b, thence through 91), 10b, and 11b to chamber So, thenthrough 9c, 10c and to chamber 6d, while the concentrated acid may bedelivered through pipe 911, over-flow device 10d, and pipe 11d to anysuitable point for further disposition. The several pipes 9a, 9b, etc.,preferably lead from the lowermost portion of the respective chambers soas to permit draining or flushing of said chambers through the over-flowdevices as hereinafter described, while the pipes lla, 11b, etc., mayopen into said chambers at any suitable height below the normal level ofthe acid therein.

Any suitable type of furnace or combustion chamber 15 may be provided,having burner means 16 for the combustion of fuel and being connected byflues 1'! to the gas delivering pipes 20 leading into the acid chamber6d. The hot gases are preferably forced through the apparatus underpressure by supplying air under pressure through flue 16' to furnace I5.

Connection from flue 1'7 to the pipes 20 may be provided by'means ofshort connecting pipes 18, said pipes 18 and 20 being connected bysuitable expansion joint means 19 provided with packing 21 which serveto permit expansion and contraction of said pipes without causing unduestrain thereon. The pipes 20 may extend through openings 22 in the bricklining 3, suitable packing 24 being provided around said pipes. The leadlining 2 is preferably doubled back over the edges of the steel shell 1around said opening as indicated at 25 and a sleeve 26 may be provided,being secured to said lining ,and steel shell and extending upwardlyaround pipe 20 and being secured 'at its upper end to the members of theexpansion joint 19 as at 2'7.

The pipes 20extend to a suitable depth below the normal acid level inchamber 6d, and are i open at their lower ends as shown at 30. In orderto deliver the gases from chamber 6d "to 60, the partition 5therebetween may be provided with a plurality of slanting ducts 32 whichextend from above the acid level in the first of said chambersytobelowthe acid level in the .ing ducts 37 for conducting gases from above theacid level in 6b to below the acid level in 6a, and with a baille plate38 similar to baifle plate 33. A gas exit flue 40 leads from the top-ofchamber 6a, for conducting the .hot gases. to a stack or to a suitableapparatusyforgreeovery of acid mist or vapors ther'efromhsuch as ascrubbing tower or the like.

Each of the overflow devices may be similar in construction to theover-flow device10d which is illustrated more particularly in Fig. 5.Such device comprises a tubular casing 45 having 'a base 46 and coverplate 47.. An inlet passage 48 extends through the base 46 andcommunicates with a central recess 49 therein. A drain passage 50extends downwardly from said re- 2 cess 49 through the bottom of base46, while an outlet passage 51 leads from the interior of casing 45through the wall thereof. The passage means 48, 50, and 51 may beflanged at their outer ends as indicated, for connection of pipesthereto in well known manner. An overflow pipe 53 may be provided withinthe casing 45 and having a base portion 54 engaging in recess 49. Saidbase portion and recess are preferably tapered as shown and ground so asto provide a snug fit when the overflow pipe is lowered into saidrecess. Said overflow pipe is provided with a port 55 communicating withthe inlet passage 48. The height of overflow pipe 53 may be adjusted byaddition of pipe sections or rings 56 of -varying heights at the upperend thereof, so as to regulate the height of the acid level in the tankwhich is connected to inlet passage 48. In practice the respectiveoverflow pipes are preferably made of such height as to provide for aslight decrease in acid level in the successive tanks and thus maintaina steady flow of acid through the tanks. It will be apparent that withthe overflow pipe in the position shown in Fig. 5, the acid, coming inthis case from tank 6d, will be caused to flow upwardly within said pipeand over the upper edge thereof into the interior of casing 45 and thenout through passage 51. However, by simply removing the cover plate 47and raising overflow pipe 53 out of the recess 49, communication isestablished from inlet passage 48 through said recess to drain passage50 so as to permit draining or flushing 'of the acid compartment towhich the device is connected. The overflow pipe, therefore, alsoconstitutes a removable plug for controlling flow of liquid through thedrain opening.

The manner of carrying out the process in the above described apparatuswill be apparent from the above description. Hot combustion gases areproduced under pressure in furnace l5 and. suchgases are first.delivered at suitable pressure through pipes 20 beneath the surface ofthe liquid in chamber 6d. In bubbling up through this body of acid thegases agitate and directly and internally heat the same and carry offwater vapor therefrom, together with some acid fumes. These gases thenpass through ducts 32 to chamber 60, wherein this process is repeatedand so on through the chambers 6b and A continual flow of acid ismaintained through the chambers in the reverse direction, the rate ofsuch flow being controlled by the rate at which dilute acid is suppliedto the apparatus through pipe 8, and the proportion of concentrationeffected in each chamber being regulated by controlling the depth ofacid therein by means of the overflow devices above described.

As stated above, it may be advantageous in some cases to depart fromstraight counter-current flow of gases and acid, to the extent ofpassing the hot gases first through a less concentrated body of acid inorder to partially cool such gases before delivering the same to themost concentrated acid. This may be accomplished in the apparatus abovedescribed by substituting pipes 12b, 12c, and 12d, (as shown in dottedlines in Fig. 1) for the pipes 11b, 11c, and 11d, so that the acid iscaused to pass from chamber 617 to chamber 6d, and then to chamber 60.The gases thus pass first through a less concentrated body of acid inchamber 6d and then through the most concentrated acid in 60.

In the apparatus shown in Fig. 6 the chambers 6a, 6b, 6c and 6d are allprovided within a single cylindrical tank provided as before with leadlining 61 and acid proof brick lining 62. Said chambers are separated asbefore by means of partitions 63 provided with inclined ducts 64'extending from above the acid level in each chamber to below the acid inthe next succeeding chamber. Bailie plates 65 are also providedasbefore. The remainder of the apparatus is substantially the sameasabove described.

A further modification of the apparatus is shown in Figs. 7 and 8 inwhich the successive bodies of acid are contained in separatecylindrical tanks 68 lined as before with lead 69 and acid proof brick70, and placed side by side. While I have shown only three chambers 6a,6b, and 6c in this case it will be understood that any suitable numberof chambers may be used in any of the forms of the invention. The hotgases are delivered, as before, beneath the surface of the acid in thechamber 60,- as by means of a plurality of pipes 72, while pipes 73extend from the upper portion of chamber -60 to'the lower portion ofchamber 611, and pipes 74 from the gr pper portion of chamber 6b, to thelower portion of chamber 6a. Pipes '15 conduct the gases away from theupper part of chamber 6a. Baflle plates {76 may be provided forpreventing entrainment of liquid acid from one chamber tothe next. Pipes8, 9a, 11a, 91), 11b, 90, and 110 and overflow devices 10a, 10b, and 100are provided, as before, for effecting and controlling flowof acidthrough the successive chambers.

Certain features of this invention may be advantageously applied inconjunction with the well known tower process of sulphuric acidconcentration. For example, one or more of the acid chambers of any ofthe forms above described may be placed ahead of the concentrating towerin an apparatus such as shown, for example, in the patent toHechenbleikner 1,456,874, and the acid may be passed first through thetower and then through said chamber. or chambers, while the hot gasespass first through thechambers in the same manner as above described,and then upwardly through the tower in contact with the acid.

An advantage of this invention is the absence of exposure of a smallstream of acid to gases at high temperature or to highly heated checkerwork structures, as in the ordinary tower process. The tower usuallyemployed in such process consists of a checker work of acid proof brickand a relatively small stream of acid is allowed to flow downwardlythrough such checker work while'the hot gases pass upwardlytherethrough. The acid flow is frequently irregular in different partsof the tower, and portions of the checker work often become over-heatedso that when acid is again brought into contact therewith, decompositionresults, particularly in the presence of hydrocarbons such as arepresent in sludge acids. This decomposition is not only substantiallyeliminated by the practice of this invention, without the use of atower, but is also minimized by the combination of this invention withthe tower process as above described, since in that case the hot gasesare first cooled by one or more passages through the acid beforebringing the same into contact with the acid in the tower.

While I have for the sake of concreteness described my invention in itsparticular application to the concentration of sulphuric'acid, it willbe understood that it' is also applicable to the concentration of acidsby means of acid vapors generally, and further, to the concentration ofliquids by means of gases, generally.

I claim:

1. The method of concentrating sulphuric acid by direct internal heattreatment which consists in maintaining a plurality of separate bodiesof acid, continuously passing acid through said bodies in succession andcausing a stream of hot gases to be successively delivered to andreleased beneath the surface of the respective bodies of acid so as topass upwardly therethrough, the gases after passingthrough one of saidbodies of acid being delivered to and passed through another of saidbodies of acid.

plurality of separate chambers, and also passing a stream of hot gasesunder positive pressure successively through said chambers, said gasesbeing conducted from above the surface of the acid in one of saidplurality of chambers to beneath the surface of the acid in another ofsaid plurality of chambers, whereby the acid is heated to successivelyhigher temperatures and concentrated to successively higherconcentrations in the successive chambers in the direction of said acidflow and the gases are cooled to successively lower temperatures in thesuccessive chambers in the direction of gas flow therethrough.

4. The method as set forth in claim 3, in which the direction of gasflow to the successive chambers is reverse to the direction of acid flowtherethrough.

5. An apparatus for concentrating sulphuric acid by direct internal heattreatment comprising means defining a plurality of chambers, means forpassing acid through said chambers in series, a furnace for producinghot gases and conduits for allowing said hot gases to pass underpositive pressure successively through said chambers and for causing thegases to pass from above the acid level in one of said chambers to belowthe acid level in another of said chambers in the direction of gas flow.

6. An apparatus for concentrating sulphuric acid by direct internal heattreatment compris-- ing a plurality of cylindrical metal tanks linedwith acid resistant material, liquid conducting pipes connecting saidtanks in series and provided with means for maintaining a definiteliquid level in each tank, and gas conducting pipes connecting saidtanks in series and extending from above the liquid level in one tank tobelow the liquid level in another tank.

'7. In an apparatus for concentrating sulphuric acid by direct internalheat treatment, means defining two chambers, a furnace device forproducing hot gases and a conduit for allowing said hot gases to flowinto the lower portion of the first chamber, means for conducting hotgases from the upper portion of the first chamber to the lower portionof the second chamber, means permitting-outflow of gases from the upperportion of said second chamber, and means for delivering acid to saidsecond chamber, for passing acid from said second chamber to said firstchamber, and for conducting acid away from said first chamber.

8. The method of concentrating sulphuric acid by direct internal heattreatment which consists in maintaining the acid in separate bodiesdefining a plurality of separate stages, in flowing the acid throughsaid stages serially for progressively increasing concentration, and inflowing in maintaining the acid in separate bodies defining a pluralityof separate stages, and in producing hot gases in a furnace device,introducing said heated gases serially through and beneath the surfacesof the acid bodiesin said plurality of stages, the gases being deliveredto each of the acid bodies below the surface thereof so as to passupwardly therethrough, and said gases after flowing through the acidbody in one of said stages being delivered to the acid body in anotherof said stages.

10. The method of concentrating a liquid by direct internal heattreatment which consists in maintaining a plurality of separate bodiesof the liquid, continuously passing the liquid through said bodies insuccession; and causing a stream of hot gases to be successivelydelivered to and released beneath the surface of the respective bodiesof liquid so as to pass upwardly therethrough, the gases after passingthroughone of said bodies of liquid being delivered to and passedthrough another of said bodies of liquid.

11. The method of concentrating a liquid by direct internal heattreatment which comprises passing such liquid successively through aplurality of separate chambers, and also passing a stream of hot gasesunder positive pressure successively through said chambers, said gasesbeing conducted from above the surface of the liquid in one of saidplurality of chambers to beneath the surface of the liquid in another ofsaid plurality of chambers, whereby the liquid is heated to successivelyhigher temperatures and concentrated to successively higherconcentrations in the successive chambers in the direction of liquidflow and the gases are cooled to successively lower temperatures in thesuccessive chambers in the direction of gas flow therethrough.

12. An apparatus for concentrating a liquid by direct internal heattreatment comprising means defining a plurality of chambers, means forpassing liquid through said chambers in series, a furnace for producinghot gases and conduits for allowing said gases to pass under positivepressure successively through said chambers and for causing the gases topass from above the liquid level in one of said chambers to below theliquid level in another of said chambers in the direction of gas flow.

13. In an apparatus for concentrating a liquid by direct internal heattreatment, means defining two chambers, a furnace device for producinghot gases and a conduit for allowing said hot gases to flow into thelower portion of the first chamber, means for conducting hot gases fromthe upper portion of the first chamber to the lower portion of thesecond chamber, means permitting outflow of gases from the upper portionof said second chamber, and means for delivering liquid to said secondchamber, for passing liquid from said second chamber to said firstchamber, and for conducting liquid away from said first chamber.

14. The method of concentrating a liquid by direct internal heattreatment which consists in maintaining the liquid in separate bodiesdefining a plurality of separate stages, in flowing the liquid throughsaid stages serially for progressively increasingconcentration, and inflowing heated gases serially through and beneath the surface of theliquid bodies in said plurality of stages for effecting a progressiveconcentration of said liquid, the gases being delivered to each of saidgases after flowing from the liquid body in said heatedgases seriallythrough and beneath the surfaces of the liquid bodies in said pluralityof stages, the gases being delivered to each or the liquid bodies belowthe surface thereof so as to pass upwardly therethrough, and said gasesafter flowing through the liquid'body in one of said stages beingdelivered to the liquid body in another 01 said stages.

WILLIAM C; MAST.

